There's a method to my madness...
Get the slot # the item is in, then set the slot contents to null, instead of the ItemStack object itself.
That UI looks very familiar... :p
What do you mean it doesn't work? Nothing happens, or you get an error? If you get an error, can you share it here?
A nether star isn't a block, so it can't be spawned as a falling block.
(At least as far as I've tested...)
Set<String> keys = //code to get your keys
int result = new Random().nextInt(keys.size());
String key = (String) keys.toArray()[result];
You would need a plugin to do this for you. Vanilla scoreboards have no way of counting online players. (At least as far as I know.)
Run /effect <Player Name> HEALH_BOOST 0 if it's normal health, or /effect <Player Name> ABSORPTION 0 if the extra hearts are gold. The Fancy Whale
Never bothered with changing the way sneaking effects the name, so I simply made an assumption! (Hence "as far as I know" ;))
Other than the title, nope!
Scores in a scoreboard require a numeric value. (Hence "scoreboard".)
NameTag behaviors are fully client-side, so as far as I know, nope.
Loop through all players on the server (or in a list, depending on what you're going for) and compare the distance of them to the specific...
Separate names with a comma.